Ruislip Woods is a Site of Special Scientific Interest and national nature reserve covering 726 acres (294 ha) in the London Borough of Hillingdon. The woods became the first national nature reserve in an urban area of England in May 1997, receiving the Green Flag Award in 2006. Ruislip Local Nature Reserve at TQ 090 899 is part of the national nature reserve.
Evidence of Bronze Age settlements has been found within the woods during archaeological excavations. Timber from the woods has been used in the building of several nationally significant buildings, as well as locally; the Great Barn at Manor Farm was built from oak from the woods.
Ownership of the woods passed with the manor from Ernulf de Hesdin to the Bec Abbey and on to King's College, Cambridge over the years, until Park Wood was sold to the local authority. The remaining woods were purchased from other owners and Ruislip Woods was formed.